AKIPRESS.COM - The U.S. and other world powers struck a landmark deal with Iran over its nuclear program this week, and the agreement might benefit one group that the U.S. hadn't counted on – the Islamic State, Business Insider reports.

Hassan Hassan, an associate fellow at the think tank Chatham House and coauthor of the recent book "ISIS: Inside The Army of Terror," said that the nuclear deal could make already-disaffected Sunnis feel even more like the U.S. and Iran are conspiring against them.

"ISIS will benefit a lot from this deal; segments of the Sunni community in the region will see Iran as having won and brought in from the dark," Hassan said.

The Islamic State, a Sunni terror group, already capitalizes on Sunni grievances for recruitment and support. ISIS presents itself as the sole protector of Sunni populations in Iraq and Syria, where Shia-aligned regimes dominate.

And conspiracy theories about U.S. collusion with Iran, a Shia theocracy, add fuel to the flames as Iran expands its influence across the Middle East.

"ISIS has already convinced a number of Sunni tribes that the Iranians are already establishing the Shia crescent," and Sunni interests won’t be protected, Christopher Harmer, a senior naval analyst at the Institute for the Study of War, told Business Insider last month.

Allowing Iran to maintain its nuclear program, albeit a curtailed and controlled version of it, isn't likely to make Sunnis rest easy. While the deal is designed to prevent Iran from acquiring a nuclear weapon, some are skeptical about whether Iran will hold up its end of the bargain.

There's also concern about the sanctions relief that comes with the deal – Iran is already pouring billions of dollars into proxy conflicts in Iraq and Syria, and the extra money that will come with an easing of western sanctions might be used to ramp up Iran's participation in these conflicts.

President Barack Obama has assured skeptics that the money from sanctions relief will be spent on growing the Iranian economy, but Eli Lake reported last month that Iran is spending much more to support the embattled regime of Syrian dictator Bashar Assad than the Obama administration has ever acknowledged.

Iran also puts significant resources into fighting ISIS in Iraq. The Shia militias Iran supports and, in some cases controls, have become one of the most effective ground forces against the Sunni extremists.

Even though the militias are fairly effective at driving ISIS terrorists out of cities, the militia fighters themselves have been accused of burning down Sunni villages and committing atrocities against civilians, which only serves to widen the gulf between Sunnis and Shias.

And even in some cases where there isn't outright violence against Sunni civilians, militia members have reportedly refused to let many Sunnis back into their homes after ISIS has left their cities.

This is all what ISIS wants. The group thrives on sectarian chaos and hopes to drive Shias to commit atrocities so that Sunnis who might have previously turned against ISIS will be forced to live with the extremists, lest they make enemies of both ISIS and the militias.

"Much of Iran’s funding in Syria has gone toward arming predominantly Shia proxies – notably the so-called National Defense Force, an IRGC-QF-built super-militia – which fight Sunnis on behalf of Assad," Michael Weiss and Nancy Youssef wrote for The Daily Beast. "An outgrowth of the sectarianism inherent in the Iranian and Syrian regime’s counterinsurgency has been ISIS, which draws thousands of Sunnis seeking to shield themselves from what they view as Shia jihadists."